Adjustable keyboard supports which may be mounted under a work surface are generally known. One example of such a keyboard support is disclosed in U.S. Pat. No. 4,826,123 to Hannah et al. The keyboard support disclosed in the '123 patent is mounted on a sliding track attached to the underside of a work surface such as a desk. A rear housing is pivotally coupled to a front housing by a parallel link mechanism. A keyboard support platform is pivotally connected to the front housing. A gas cylinder is used to provide motive power in raising the keyboard support platform and manual force is required for lowering the support platform. The gas cylinder is actuated by a rod passing through the link assembly and bears on an activating button at the end of the gas cylinder. The keyboard support mechanism of the '123 is directed to positioning the keyboard platform in front of and below the work surface.
The present invention, on the other hand, provides a support mechanism which permits the user to position the keyboard support platform not only in front of the work surface but also well above the work surface. Thus, the operator may move the support platform to a position high enough for the operator to use the keyboard while standing. Unlike prior art mechanisms which require activating levers or friction locks to release or set the position of the keyboard support platform, the position of the platform in the present invention is maintained by a self-locking gas cylinder within a parallel linkage. The gas cylinder is adjusted to provide sufficient counterbalancing force to the weight of the keyboard, keyboard support platform, and parallel linkage assembly.
By counterbalancing the weight of the support assembly and utilizing a self-locking gas cylinder, the present invention eliminates or reduces the need for a separate locking mechanism and provides substantial ergonomic advantages over the prior art. Less manipulation of the device is required by an operator and the keyboard support mechanism is therefore more likely to be oriented in an ergonomically desirable position. In contrast, if operators are required to loosen or tighten various locking mechanisms, they may be reluctant to alter the orientation of the platform and thus risk injury from typing on the keyboard in an awkward and harmful position.
The invention provides an ergonomically adjustable sit/stand keyboard arm apparatus. The apparatus is slidably mounted on the underside of a work surface such as a table. A first rotatable housing depends from the sliding mount. The first housing is connected to a second housing by a parallel linkage means. A keyboard platform is rotatably mounted on the second housing. An extender is provided between the second housing and the keyboard platform to raise the keyboard platform to sufficient height for use by the operator while standing and to permit the arm to be lowered below a generally horizontal orientation. The keyboard platform is maintained in position by a self-locking pneumatic cylinder and an adjustable cylinder assembly for counterbalancing the load on the parallel linkage mechanism.
The invention will be more fully understood from the following detailed description of the preferred embodiments which should be read in light of the accompanying drawings.